Rotary underreamer



Oct. 8, 1 0- J. c. STOKES ROTARY UNDERREAMER Filed April 6, 1959 on p Patented on a, 1940" PATENT OFFICE noraar UNDERREAMEB John 0. Stokes, Houston, Tex., minor to Deed Roller Bit Company, Houston, Tex, a corporation of Texas Application April 6, 1939, Serial No. 266,313

2 Claims.

This invention relates to a rotary underreamer and has 'for its general object the provision of a means for supporting and. actuating the cutting parts thereof.

Rotary underreamers have been designed in the past in which the cutting parts or blades have i been expanded in various ways, both mechanical and by fluid pressure, so that the underreamer could ream out a well hole below the lower end of a casing therein to a diameter larger than the casing itself. However, difficulty has in the past been encountered in that it has been impossible in many cases for the operator at the surface of the earth to tell whether an underreamer which has been lowered into a well has its blades in expanded position so that drilling may proceed or whether the blades are folded or moved inwardly to an inactive position or to a position of smaller diameter. 'I'heresult of this has been that in many cases an underreamer would fail to operate properly and might actually be ruined by an attempt to drill therewith when the cutting parts were not properly expanded.

It is, therefore, an object of this invention to provide a rotary underreamer of such a nature that an operator at the surface of the earth will be able to determine with a high degree of certainty at any particular time whether the cutting parts thereof have been expanded to active or cutting position.

Another object of this invention is to provide a rotary underreamer the blades of which will be expanded and locked in expanded position by fluid pressure but which will not be retracted when the fluid pressure ceases.

Another object of this invention is to provide a rotary underreamer of such a nature that fluid under pressure in substantial quantities may be pumped through a drill stem to which it is attached only when the cutting parts are in expanded position.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawing, wherein is set forth byway of example only one embodiment of this invention.

In the drawing:

Fig. 1 is a view partly in vertical cross section and partly in side elevation, illustrating a rotary underreamer constructed in accordance with this invention, with the cutting blades thereof in retracted or inactive position.

Fig. 2 is a similar view showing the cutting parts in expanded or active position Fig. 3 is a horizontal cross section taken along the line 3-3 of Fig. 2.

Fig. 4 is a bottom plan view of the device shown in Fig. 3.

The underreamer constructed in accordance with this invention is adapted to be secured to the lower end of a drill stem I of any conventional constructionby means of threads 2. The body 3 on which the threads 2 are formed is provided with a lower part 4 of enlarged external and internal diameter, and is externally threaded at its lower end as indicated at 5 for the reception of the reamer head 6. Thereamer head 6 within its upper end is provided with an opening having an upwardly facing shoulder 1 against which is seated a corresponding shoulder on a liner 8. Resting on the upper end of this liner and secured in place by contact with the lower end of the body 3 is a disc-like element 9 having fluid passages Ill therethrough at points spaced about its outer periphery and having a similar opening ll therethrough for the reception of a plunger stem or guide I2. The disc 9 is also slightly countersunk on its upper side as shown at l3 for the purpose of receiving and positioning the lower end of the compression coil spring I! which surrounds the stem 12. The upper end of this spring It bears against a washer l5 which in turn is held inplace on the stem l2 by means of nuts [6 threaded onto the upper end thereof. on its lower end, this stem I2 is adapted to receive the piston-like elements l1 and I8, the element l8 being provided with a channel for the reception of a U-shaped packing ring I9. This packing ring l9 fits snugly within a cylindrical lower part of the reamer head 6.

The element I8 is illustrated as being threaded to the lower end of the stem l2 at 2| and prevented from becoming unscrewed from the stem by means of a cotter key 22 or the like. This element is also provided with a pair of downwardly extending spaced arms 23 which are substantially parallel and are adapted to receive the blades 24 and 25 between them. Each of these blades 24 and 25 has an opening 26 therethrough and a pin 21 is extended through these openings in the blades and the arms 23 and threaded into one of them so as to secure the blades 2| and 25 to the element I8. The openings 26 in the blades are in each instance of elongated form, the length of the respective openings being equal to the maximum distance traveled by the piston comprising the elements l1 and [8. Each of these openings also has an oiiset portion 28 so as to permit the blades to move laterally with respect 5 to the pin 21 when the pin is so. located that it may enter these portions II of the openings 20.

Each of the blades is provided with a lower cutting portion 29 and with an upper or shank portion 3.. The openings 28 are formed in these shank portions and each shank portion is provided also with laterally extending ears 3| and 32 adapted to engage the upwardly facing shoulder 33 within the reamer head I, when the blades are in their lower or expanded position as illustrated in Fig. 2. The blades are held in snug engagement with each other and prevented from vibration or lost motion between the arms 23 by means of springs 34 located in countersinks in the respective blades and bearing against the inner surfaces of the respective arms 13.

In operation, the device is lowered into a well hole through a casing therein with the parts in the position shown in Fig. l. The plunger consisting of the elements l1 and It will be retained in its upper position as shown by means of the spring l4 and the blades 24 and 25 will be prevented from expanding both by the slight frictional engagement caused by the springs 34 and by the fact that they cannot expand so long as the tool is within the casing. When the tool has been lowered to a point below the casing and it is desired to begin drilling or reaming, the slush pumps will be started and slush forced into the drill stem I under pressure. This pressure will act upon the upper portion of the piston and tend to force the same downwardly. So long as the piston remains in the position shown in Fig. 1, however, very little slush can flow downwardly through the drill stem because of the fact that the element l1 substantially shuts oil! or greatly reduces the area available for slush flow from the drill stem. 11, therefore, the blades or any other part of the device shall have become stuck, or if due to some obstruction the blades cannot open or expand, the pin 21, together with the piston will be prevented from moving downwardly and the pump which is adapted to pump slush through the drill stem will either stall or operate only at a very slow speed. This will notify the operator or driller that the blades have not expanded and are not in position for drilling. If and when the blades do expand, they will move to the position shown in Fig, 2 in which position the elongated portions of the openings 26 will be in alignment and will permit the downward movement of the pin 21 and the piston, whereupon the element I! will substantially clear the enlarged portion 35 within the reamer head 6 so that slush may pass from the drill stem downwardly into this portion 35 and thence into and through the slush passageways 38 leading downwardly therefrom. When this occurs, the slush pump will operate freely and the, driller will know that the blades have expanded and that the device is in position for drilling. He may then proceed with the drilling in the usual manner.

When the drilling is completed the slush pump is stopped or pressure in the drill stem is otherwise relieved so as to permit the spring l4 to move the piston upwardly. Inasmuch as the elongated portions of the openings 26 in the blades are of the same extent as the possible movement of the pin 21, the piston and this pin may move upwardly to an upper limit of movement without, however, disturbing the expanded position of the blades 24 and 25. The pin 2'! under these circumstances will simply move upwardly to the upper ends of these openings and the blades will remain in expanded position. However, when the device is pulled upwardly these blades will come in contact with the lower end of the casing and will be moved thereby downwardly and inwardly. This will cause the shanks of these blades to move to the position shown in Fig. 1 wherein the pin 21 lies in the lateral extension 28 of each of these openings. The device may then be withdrawn from the well in the usual manner.

It will be seen from the foregoing that a means has been provided whereby all of the objects and advantages sought by this invention may be accomplished.

Having described my invention, I claim:

1. In a rotary underreamer, a reamer head, cutter blades carried by said head for expansion and retraction with respect thereto, each of said blades having an elongated opening therethrough, and fluid pressure actuated means for exerting an expanding force on said cutter blades, said means including a yoke adapted to straddle the slotted portions of said cutter blades, and a pin carried by said yoke and passing through said slots for movement therein, said slots and pin being so positioned relative to each other that when said blades are in expanded position said pin and said fluid pressure means may move within the maximum limits without movement of said blades.

2. In a rotary underreamer, a. reamer head, cutter blades carried by said head for expansion and retraction with respect thereto, each of said blades having an elongated opening therein, and fluid pressure actuated means for exerting an expanding force on said cutter blades, said means including a pin extending into said openings for movement therein, said openings and pin being so positioned relative to each other that when said blades are in expanded position said pin and said fluid pressure means may move within the maximum limits without movement of said blades.

JOHN C. STOKES. 

